Of course, it had to be the Daleks. When the BBC first conceived of the Doctor Who Adventures, its ambitious series of four downloadable computer games, these tenacious beings must have been at the top of the essential features list. And on 5 June, they will return, terrorising the planet right in City of the Daleks, the opening instalment.

Commissioned by BBC Wales in conjunction with BBC Online, and developed by Sheffield-based games studio Sumo Digital, the series is certainly getting off to an explosive start. The Daleks have altered time to invade Earth in the year 1963 (intriguingly, the year Doctor Who first aired). When the Tardis arrives, swinging London has been utterly destroyed and the last living human is sheltering in Charing Cross underground station. Amy and the Doctor must now repair the continuum to prevent the invasion, or the Doctor's new assistant will fade out of existence. The problem is, the task will require a dangerous trip to Skaro, the Dalek home planet, and more specifically the looming metropolis at the core of their empire. Hence, the title.

Featuring impressive likenesses of Matt Smith and Karen Gillan (who also voice all the dialogue) the game is essentially a very polished, very intuitive action adventure, designed with families very much in mind. "We felt that Doctor Who was perfect for a game – the TV series has so many parallels with games," says Ian Tweedale, editor of interactive at BBC Wales. "Also, although the game is great for young people who are already game players, we wanted to bring in a mass TV audience, people who may not play games, and introduce them to what games are about, and maybe whet their appetite to try more."

The start point of City of the Daleks is an impressively destroyed Trafalgar Square, all collapsed monuments, smoking buildings and deep chasms leading to the fractured underground train lines below. You move the doctor by controlling his direction with the mouse and clicking the right button to walk. But watch out, there are Daleks all over the place.

And here is where the development team faced a significant hurdle, more-or-less unheard of in game production – the Doctor is a devout pacifist. There will be no AK47 gunfights, no frag grenades. As Sean Millard, creative director at Sumo, puts it: "The Doctor saves humanity and solves all the problems of the universe through the power of negotiation and clever quips – which in themselves don't make for great gameplay. It would be brilliant if he had a lightsaber, or twin guns, but he hasn't. There was a lot of design time spent working out how interaction with the baddies could be made fun."

Consequently, the action sequences are based around a stealth mechanic. Your first job is to sneak past a group of Daleks patrolling the area – their sphere of vision is shown as a green area, which you've got to avoid. Step inside the green and it goes to amber, then red, and they know you're there – cue first use of the phrase "exterminate".

From here it's a mix of exploration and environmental puzzles. You've got to get through a barricade barring entry to the underground station, and a precariously balanced taxi on a steep incline in front of the barrier would seem to be the solution. Whenever you approach a relevant scenic item, an icon pops up in the bottom right offering an action – "climb" perhaps, or "talk". Clicking the left button carries it out. Most of the actions are context sensitive so you don't have to worry about learning lots of moves. And if you talk to Amy she'll usually reveal your current objective. The jokey interplay between these characters has been nicely reproduced, especially in the short movie segments between each playable area. For example, before the duo arrive in London the Doctor asks Amy which Beatle she'd most like to meet. When she replies "John or Paul", he asks why no one ever says Ringo. "There's no such thing as a sexy drummer," is her damning response.

The Doctor gets a small inventory of items to carry around, and naturally, this includes, the sonic screwdriver, which brought in its own range of problems for the game designers. "It's very important in a game to have a strong internal logic," says co-producer Charles Cecil, a veteran designer of adventure titles like the famed Broken Sword series. "We spent a lot of time asking what exactly does a sonic screwdriver do? In a game players need rules that they can totally understand."

"I'm not sure we ever got an answer to that," adds Millard. What the device DID mean was that the traditional video game means of barring a player's progress – the ubiquitous locked door – couldn't be used: the sonic screwdriver is a skeleton key. Instead, players will find that they must often solve logic puzzle-style mini-games to make progress. These may involve re-arranging circuit boards, or carefully removing sensors from the electrified innards of a Dalek's head unit. And these get tougher as the game goes on.

The 3D visuals are hardly cutting edge, but that's not the point. The game has been designed to be playable on almost any PC or Mac hardware – the target platform is apparently an entry-level PC from four-years ago ("We've been testing it on BBC computers, which are, as you'd expect, the oldest in the world," deadpans senior BBC Wales Interactive producer, Matt Fidell). Also, there's a nicely stylised look to the two leads – and much of their character has been captured, right down to Matt's distinctive loping stride (the developers spent a day in London filming him just walking about).

The environments, meanwhile, have perfectly captured the extravagantly coloured lighting and offbeat steam punk technologies of the series. Most of the backgrounds are produced as beautifully detailed 2D illustrations, which are mapped around the 3D environment. It's a beautiful, slightly retro effect harking back to Cecil's Broken Sword adventures, and particularly effective when the Doctor reaches Kaalann – the Dalek city. The planet has not been visited during the reboot of the TV series, and has never been fully visualized before.

That, says Tweedale is the key beauty of developing a game based on the brand. "There are bits we can do in the game that we just can't do on TV, like having Trafalgar Square smashed up by the Daleks. We couldn't do that on television, even with CGI, it's just too expensive. Here, we can go to Skaro, we can envisage all sorts of things we couldn't do before."

The game's writer, Phil Ford, has scripted episodes of Torchwood, Doctor Who: Dreamland and Sarah Jane Adventures. He was equally excited about the chance to explore new territories. "Every episode takes us to somewhere we couldn't do on TV. Everyone was really fired up that we would be able to go to Kaalann. That's why I like to do these animated spin-offs – they give you the opportunity to really broaden the Doctor Who canvas."

A key element of the development process seems to have been the cross pollination of ideas between the Doctor Who team and the game developers. Usually, when a studio is developing a game tie-in with a major TV or film brand they have to slavishly adhere to the original design vision. Not here. For the design of Kaalann for example, the Sumo Digital artists were given just a one word brief by Steven Moffat and his team: brutal. Their original concept sketches were all sleek high-tech skyscrapers, but, along with the BBC team, they felt the city looked too human. Someone from the TV series suggested Fritz Lang's Metropolis as an influence, and Sumo took this in a whole new direction. The result is a dense Art Deco-style cityscape beneath a raging orange sky.

It's an impressive creation, and better yet, it has become canon. If the TV series ever comes to Skaro, the BBC design team will use the version seen in the game. Indeed, this crossover is already happening. At some point a scene used in the games will also appear in the current Doctor Who TV series, so the game team were invited on set. "We thought we were just going there to see what the sets would be like, but it turned out the designers were altering the sets to fit what we wanted in the game, which was a bit of a shock," says Cecil. "Right from the beginning we've worked very closely. There's been amazing co-operation."

Even the actors are getting in on this sense of crossover. As Nicholas Briggs, the voice of the Daleks, explains: "The red Dalek speaks a lot in the game, whereas in the TV series, in Victory of the Daleks, the red Dalek doesn't say anything. So I had to come up with my red Dalek voice, which I will be using should the red Dalek ever re-appear!"

The Sumo Digital team reckons there's around two or three hours of gameplay per episode, if you rush straight through the linear narrative. However, players who spend a little longer exploring the environments will find a selection of collectible cards featuring Doctors of the past, as well as well-known enemies, allies and differently coloured jelly babies. Apparently, the each game is a 250MB file, which is less than downloading an episode of the TV series. While the first episode is out on 5 June, the others are likely to follow on a monthly basis. They are all separate stories, but Millard reckons you'll get a more rounded experience playing them in sequence.

The BBC has no idea what to expect from here. It's the first time the corporation has commissioned an interactive project of such size, and it could well open the doors to similar projects with other big brands. For now though, Doctor Who fans will have a thoroughly enjoyable experience, jumping into the shoes of their favourite Timelord and attempting to outwit the Daleks. Once they are beaten, the subsequent three adventures are likely to feature more of the Doctor's classic foes. Indeed, we've seen some concept art from another of the games – it features an Arctic science research base and some very familiar giant robots. Yes, the Cybermen are coming …